标题： 红巨星演化状态的光学光谱特征 显示英文标题

标题： Optical spectroscopic signatures of the red giant evolutionary state

摘要： 现代光谱巡天输出大量数据。 理论模型提供了一种手段，可以将这些数据中编码的信息转化为物理恒星属性的测量值。 然而，具体而言，这些模型是不完整的且简化的，并且限制了我们对光谱细节的解读。 相反，可用的数据提供了一个机会，可以使用基于数据的、差异化的分析技术，作为一种理解光谱特征的方法。 我们部署了这种分析方法来研究核心氦燃烧红团簇（RC）和壳层氢燃烧红巨星分支（RGB）恒星，以揭示光学恒星光谱中留下的演化状态特征。 我们利用来自GALAH巡天的786对RC和RGB恒星，选择时尽量最小化光谱差异，并结合TESS和K2振荡学的演化状态分类。 我们报告了这两类恒星之间千分之一量级的残余系统光谱差异，并表明与使用相同标准选择的参考样本中的RC$-$RC和RGB$-$RGB对相比，这些残差具有显著性。 首先，我们报告了由于恒星演化和质量差异引起的Swan ($\rm{C}_2$)带以及CN带的系统差异，其中具有相似恒星参数的RGB恒星的质量高于RC恒星。 其次，我们观察到H$_{\alpha}$和H$_{\beta}$线宽的系统差异是由微湍流差异引起的，根据GALAH测得的微湍流显示，我们测量到RC恒星的微湍流比RGB恒星高。 这项工作展示了大型巡天通过无模型、基于数据的方法揭示恒星演化微妙光谱特征的能力。 显示英文摘要

摘要： Modern spectroscopic surveys output large data volumes. Theoretical models provide a means to transform the information encoded in these data to measurements of physical stellar properties. However, in detail the models are incomplete and simplified, and prohibit interpretation of the fine details in spectra. Instead, the available data provide an opportunity to use data-driven, differential analysis techniques, as a means towards understanding spectral signatures. We deploy such an analysis to examine core helium-fusing red clump (RC) and shell hydrogen-fusing red giant branch (RGB) stars, to uncover signatures of evolutionary state imprinted in optical stellar spectra. We exploit 786 pairs of RC and RGB stars from the GALAH survey, chosen to minimise spectral differences, with evolutionary state classifications from TESS and K2 asteroseismology. We report sub-percent residual, systematic spectral differences between the two classes of stars, and show that these residuals are significant compared to a reference sample of RC$-$RC and RGB$-$RGB pairs selected using the same criteria. First, we report systematic differences in the Swan ($\rm{C}_2$) band and CN bands caused by stellar evolution and a difference in mass, where RGB stars at similar stellar parameters have higher masses than RC stars. Secondly, we observe systematic differences in the line-width of the H$_{\alpha}$ and H$_{\beta}$ lines caused by a difference in microturbulence, as measured by GALAH, where we measure higher microturbulence in RC stars than RGB stars. This work demonstrates the ability of large surveys to uncover the subtle spectroscopic signatures of stellar evolution using model-free, data-driven methods.